The present invention relates to a sheet feed cassette which is equipped in an image forming apparatus such as a copying apparatus or a printer, and especially relates to a structure of the sheet feed cassette in which a large-sized recording sheet such as size A3 or A2 can be loaded.
Generally, in an image forming apparatus such as a copying apparatus or a printer, recording sheets of sizes of, for example, B5, A4, or B4 are frequently used and a plurality of sheet feed cassettes in which these recording sheets are loaded separately according to their sizes, or a universal cassette in which different sized recording sheets are loaded together, are equipped. When large-sized recording sheets such as A3 or A2 are used, large-sized sheet feed cassettes in which these recording sheets can be loaded are prepared for the image forming apparatus.
However, for example, when an A2 sized recording sheet is loaded, a conventionally used large-sized sheet feed cassette is inevitably larger than size A2 when a guide member or a regulation member for conveyance is included in the cassette. That is, it is large, heavy, its handling property is not good and its manufacturing cost is high.
The first object of the present invention is to solve the above-described problem and to provide a sheet feed cassette for an image forming apparatus which is light, has good handling property, and is low cost even when a large-sized recording sheet such as A3 or A2 is loaded.
Further, when the large-sized cassette is used with a publicly known ADU (Automatic Duplex Unit) which is built into the image forming apparatus, there is a problem that the image forming apparatus inevitably becomes large. Therefore, the present invention relates to an intermediate stacker on which a large-sized recording sheet such as a sheet of size A2 can be stacked, in the case of the image forming apparatus in which an ADU having the intermediate stacker is provided, wherein recording sheets, one side of which has been copied, are stacked on the intermediate stacker prior to two-sided copying.
Generally, when recording sheets apart from those commonly used are used, it is necessary to prepare a sheet feed cassette for exclusive use. Especially when a large sized recording sheet such as A2 is used, not only a large-sized sheet feed cassette is necessary, but also it is necessary to move the image forming apparatus itself or other apparatus in order to equip the sheet feed cassette in the image forming apparatus.
In order to solve these problems, intermediate stackers mounted in the image forming apparatus, by which two-sided copying can be performed, used as sheet feed units, have been proposed in the specifications of Japanese Patent Publication Open to Public Inspection Nos. 205548/1985 and 151555/1986. In these proposals, different size recording sheets which are commonly used can be loaded in the stacker. However, a large-sized recording sheet such as A2 can not be loaded therein.
The second object of the present invention is to provide an image forming apparatus in which the intermediate stacker provided in the ADU can be used as a sheet feeding unit for a large-sized recording sheet as a result of improvement of the forgoing problems.